1. Technical Field
The present application relates to an apparatus and method for tracking defects in sheet materials.
2. Background Information
Background information is for informational purposes only and does not necessarily admit that subsequently mentioned information and publications are prior art.
The present application relates to a method and an apparatus for marking a material defect in a sheet material.
During the processing of sheet materials, such as, for example, metal sheets, paper sheets, or also plastic films, the sheet materials are unrolled, then guided through the respective processing stations, and then rolled up again or, for example, divided into sections.
During guiding through the processing stations, the sheet material is examined for material defects. For example, an optical examination may be carried out on the sheet material, and then any defective points can be marked for identification. For identification, for example, color markings can be applied, or a marking substance or marker can be introduced into the sheet material.
The processing of the material defect usually takes place after the running through the processing stations or, if appropriate, in a separate work stage, in which the sheet material is again unrolled. In any event, the sheet material runs through numerous stations of the apparatus between the detection of the defect and the processing of the defect, such as, for example, deflection rolling. As a result of this, the markings which have been applied, which identify the material defect, are frequently altered or removed, such that the position of the material defect cannot be determined with certainty.
In order to be able to locate the material defect despite defective identification marking, it is possible, as an alternative, to determine the run-through speed of the sheet material through the processing stations, such that, by way of a calculation, the position of the material defect can be determined or calculated. In other words, the speed at which the material is run through the system can be utilized to calculate when the portion of the sheet material containing the defect would be expected to pass or go through a certain point or area in the processing stations downstream of the defect-detection region.
Such calculation systems, however, are extremely imprecise, and with sheet materials, which, for example, are stretched or shrunk during the processing, are highly unreliable, such that reliable location of the material defect cannot be effected, or, for the processing of the material defects, it may be necessary and/or desired for substantially larger sheet sections to be processed. In other words, there are different factors that can make it difficult to reliably and consistently determine, by calculation, the expected location of the material defect downstream in processing. One factor is the general imprecision of most calculation systems. Another factor can be the sheet material itself. Some sheet materials, such as plastic film, may stretch or shrink during processing or handling of the sheet material. These different factors can affect the precision and/or accuracy of the detection and handling process.
For example, a defect-detection station or mechanism or unit could be used to inspect sheet material passing thereby or therethrough, and thus detect an area or a portion or a section of the sheet material that contains a material defect. In order to treat or process the material defect, a defect-processing station or mechanism or unit is positioned downstream of the defect-detection station. A calculation could then be performed, based on the speed of movement or travel of the sheet material through the overall sheet-handling machine, to determine or calculate or estimate when the portion of the sheet material containing the material defect will be passing by or through the defect-processing station. Using the known lengthening or stretching and speed characteristics of the sheet material related to the process which the sheet is undergoing, the computer system can approximate when and where the defect will arrive at the downstream sensing location. The processing is thus performed in essentially a “blind” manner based strictly on the calculation. In other words, a section of sheet material can be processed based on the calculation and expectation that the defect detected upstream will be in the section of sheet material in the defect-processing station at the calculated time, and not whether or not the defect is actually present in the section of sheet material being processed. Thus, if the calculation is erroneous or sufficiently imprecise, as can often be the case with many calculation systems, the defect-processing station will process a section of material that does not contain a defect, which is undesirable. Not only will sheet material of acceptable quality be processed, such as by removal, but the defect will remain in the sheet material that proceeds on for further use. Obviously, such waste of acceptable material and failure to process defective material is undesirable. In addition, if the material is generally prone to stretching or shrinking during handling, the section of the sheet material containing the defect will either arrive earlier or later at the defect-processing station than would be expected by the calculation. As a result of the imprecision of calculation and/or variability in the characteristics of the sheet material, larger amounts of material often must be processed in order to compensate for the imprecision, which can be wasteful. Thus, if no markings are available to mark exactly where a defect is in the sheet material, the user must choose either between a very imprecise detection, or a wasteful compensation process, neither of which are desirable.
As discussed above, the sheet material to be processed or handled could be different materials, such as paper, cellulose, plastic, metal, a metallic material, or other materials suitable for commercial use, such as in the container manufacturing industry or product packaging industry. The material defects could be such things as cracks, micro-cracks, tears, rips, bubbles, distortions, warping, discoloration, marks, misprints, folds, creases, wrinkles, holes, perforations, depressions, recesses, thinned portions, thickened portions, oil spots, or any other defect that would or could have a negative effect on the structural quality or aesthetic quality of the sheet material.